BACnet router configuration - Metasys - LIT-12011034 - General System Information - Metasys System - Release 11.0

MS/TP Communications Bus Technical Bulletin

Product name
Metasys System
Document type
Technical Bulletin
Document number
Release 11.0
Revision date

Configuration of the BACnet Router varies by vendor and model of the device, but several important configuration settings are required for all routers. Table 1 lists those settings and Figure 1 provides an example. For more details on BACnet Router parameters, refer to the documentation provided with your router.

Note: When you install a BACnet Router for adding a Remote Field Bus to the job site, you need a site-level, unique MS/TP network number and device object ID (if it contains a device object) for the BACnet Router. In addition, it is critical that you determine if a BACnet Broadcast Management Device (BBMD) is required for the BACnet Router. If you configure the BACnet Router as a BBMD, assign a static IP address to both the router and the SNE or NxE or ODS where you are configuring the MS/TP bus. For an existing installation, contact the BAS Manager, Building Manager, or IT department for information on available network numbers, device object IDs, and existing BBMDs for crossing IP subnets. Information on configuring a BBMD in a BACnet Router (if it supports them internally) is available from the router vendor.
Table 1. BACnet router attributes
BACnet router attribute name Description

User action or Recommended Setting

Network number (for ethernet BACnet/IP)

A unique identifier defined for the BACnet IP network connection on the BACnet Router. The network engine uses this number to locate the device.

Specify the network number assigned for BACnet/IP connections to the BACnet network. Do not use 2000 or 65000 as the network number; these numbers are used for existing embedded networks.

Note: In most cases, the IP side of the BACnet Router shares the same Network Number as all of the BACnet IP connections in one BACnet network (example: 1001). Figure 1 shows an example.

Network number (for BACnet MS/TP, Port 1)

A unique identifier defined for the BACnet MS/TP network connection on the BACnet Router.

Specify the network number for the BACnet Router on the MS/TP side with the network address specified in the Metasys network engine under which the Remote Field Bus is defined. The MS/TP side of each BACnet Router must have a unique Network Number for the site because each remote bus is a separate network (example: 2801, 2802, 2803). Do not use the same network number as any of the SNE or NAE MS/TP trunks. Figure 1 shows an example.

Device ID

The Device ID is the instance number for the BACnet Router. This number must be unique across the building networks for all device instances.

Specify a unique number.

Note: As you add routers, be sure to replace the router's default device ID with a unique value for your site. The router's device ID must be different from the device ID of all other BACnet devices at the site.

Device name

A name to identify the BACnet Router. This name must be unique across the building network.

Specify a unique name.

BACnet/IP Broadcast Management Device (BBMD)

The IP network subnets used by both the BACnet Router and the network engine normally require that you define BBMDs on each subnet if those IP subnets are different. Each IP subnet generally requires exactly one defined BBMD. Many routers include BBMD capability in order to simplify this requirement.

Enable and configure the router BBMDs with an appropriate broadcast distribution table.

MS/TP MAC address

The MS/TP MAC address of the BACnet Router you select must not conflict with any other MS/TP device on the same wire. Address zero (0) is generally recommended. For other field devices connected to the same RS-485 MS/TP bus, use sequential addressing following the Metasys MS/TP bus addressing recommendations and reserved addresses. No single MS/TP MAC address can be used by more than one device on the same MS/TP bus regardless of the type of device.


Baud rate

The RS-485 connection on the BACnet Router requires a specified baud rate in order to initiate communication with field devices that may use auto-baud rate configuration.


MS/TP Max Manager

The highest manager MS/TP node number used on the bus.


MS/TP Max Info Frames

The Max Info Frames setting on the BACnet Router you specify should be high enough to allow the transmission of at least as many MS/TP frame packets as there are available MS/TP frame buffers in the router.

80 to 100 (all devices are Johnson Controls field devices)


20 (some or all devices are third-party field devices)

Max APDU Length

The maximum size of a BACnet APDU (Application Layer Protocol Data Unit) accepted by the device. For most BACnet Routers, this is a read-only attribute that is fixed to the maximum value defined for BACnet MS/TP.


(or use default)

Router configuration password (if available)

A password that you must enter to access the BACnet Router configuration settings.

To protect from intruders, change the default password.

IP settings

The BACnet Router requires common IP communication configuration settings for the UDP port (default 47808), IP network, and IP subnet mask.

Set these appropriately for the site and the router.

Figure 1. Setting network address or network number

For BACnet/IP configuration you need to match the network number specified on the IP side of the BACnet Router with the network address specified in the device object of the engine of the OAS. See Figure 1.

For BACnet MS/TP configuration match the network number specified on the MS/TP side of the BACnet Router with the network address specified under the Hardware tab of the Remote Field Bus Integration. The network address must be unique for each remote field bus at the site. See Figure 1.